<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>let和const</title>
</head>
<body>
    
</body>
<script>
    /*
    存在异步问题,当i执行到i等于3的时候才会执行setTimeout
    */
    // for(var i=0;i<3;i++){
    //    setTimeout(function(){
    //     console.log(i);

    //    },1000*i);
    // }
    for(let i=0;i<3;i++){
        setTimeout(function(){
        console.log(i);

       },1000*i);
    }
    const pi=Math.PI;
    console.log(pi);
</script>
</html>